I. Field
The following description relates generally to wireless communications, and more particularly to spatial cycling across antennas for channel quality information (CQI) computation and data transmission in a wireless communication system.
II. Background
Wireless communication systems are widely deployed to provide various types of communication content such as, for example, voice, data, and so on. Typical wireless communication systems can be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, . . . ). Examples of such multiple-access systems can include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and the like.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple wireless terminals. Each wireless terminal can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to wireless terminals, and the reverse link (or uplink) refers to the communication link from wireless terminals to base stations. Further, communications between wireless terminals and base stations can be established via single-input single-output (SISO) systems, multiple-input single-output (MISO) systems, multiple-input multiple-output (MIMO) systems, and so forth.
In a wireless communication system, a transmitter (e.g., a base station or a terminal) can utilize multiple (T) transmit antennas for data transmission to a receiver equipped with one or more (R) receive antennas. Multiple transmit antennas can be used to increase system throughput by transmitting different data from these antennas and/or to improve reliability by transmitting data redundantly. For example, the transmitter can transmit a given symbol from all T transmit antennas, and the receiver can receive multiple versions of this symbol via the R receive antennas. These multiple versions of the transmitted symbol generally improve the receiver's ability to recover the symbol.
Transmission performance can be improved by exploiting the spatial dimension obtained with the multiple transmit antennas and, if present, the multiple receive antennas. A propagation path exists between each pair of transmit and receive antennas. T·R different propagation paths are formed between the T transmit antennas and the R receive antennas. These propagation paths can experience different channel conditions (e.g., different fading, multipath, interference effects, . . . ) and can achieve different signal-to-noise-and-interference ratios (SNRs). The channel responses for the T·R propagation paths can vary from path to path and can further vary across frequency for a dispersive wireless channel and/or over time for a time-variant wireless channel.
A major drawback to using multiple transmit antennas for data transmission is that the channel response between each pair of transmit and receive antennas (or each propagation path) typically needs to be estimated in order to properly receive the data transmission. Estimation of the full channel response for all T·R transmit and receive antenna pairs can be undesirable for several reasons. For instance, a large amount of link resources can be consumed in order to transmit a pilot used for channel estimation, which in turn reduces the link resources available to transmit data. Further, channel estimation for all T·R transmit and receive antenna pairs increases processing overhead at the receiver.